(iv) cos x - cos 2x + cos 3x - cos 4x = 0
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Answered by
6
Answer:
- cosx + cos2x + cos3x + cos4x = 0 ∴ cosx + cos3x + cos2x + cos4x = 0 ∴ 2cos2x ∙ cosx + 2cos3x ∙ cosx = 0 ∴ 2cosx(cos2x + cos3x) = 0 ∴ 4cosx ∙ cos(5x/2) ∙ cos(x/2) = 0 ∴ x = (π/2), (3π/2), (π/5), (3π/5), (7π/5), (9π/5) & π ∴ Total solution = 7.
Answered by
0
Answer:
Cosx+ Cos2x+ Cos3x+ Cos4x = 0
Cosx+ Cos3x + Cos2x + Cos4x = 0
2Cos2x . Cosx + 2Cos3x . Cosx = 0
2Cosx ( Cos2x + Cos3x ) = 0
Therefore:
4Cosx . Cos(5x/2) . Cos ( x/2 ) = 0
Total Solution = 7
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